2-Amino-4-(4-fluorobenzylamino)-1-ethoxycarbonylaminobenzene (which is known by the INN name retigabine, or its USAN name ezogabine) is disclosed in U.S. Pat. No. 5,384,330 and EP 0554 543. U.S. Pat. No. 5,384,330 discloses compounds which, can for example, be used as anti-epileptic, muscle-relaxing, fever-reducing and peripherally analgesically acting medications. Drugs of the future 1995 (2) 11:1112-1115 discloses a preparation of retigabine (D-23129). WO98/031663 (U.S. Pat. No. 6,538,151) discloses 3 different pure crystal modifications, called A, B and C. WO2010/009433 and US2010/0323016 disclose modified release formulations of retigabine. Marketing approval for retigabine as an adjunctive treatment of partial seizures has been granted in Europe and is currently being sought in the US, and other countries.
U.S. Pat. No. 5,384,330 describes two processes for making retigabine designated therein as Variant A and Variant B.